Brent Thome, a computer scientist in San Francisco, is building a
mechanical computer out of beautiful, laser-cut gears that will compute
and draw fractals. He's documenting as he goes in a fascinating blog, in
which he also recounts his adventures with kinetic wooden sculpture.

Theory of Operation
I
could tell you that it took years and years of research and development
to create a theory of computation that could be implemented in wood,
but alias it would be untrue. The idea was formed after only a few
reductions and one night when I couldn't get to sleep. You see,
computers are much simpler than our teachers might of taught us in
school. You don't even need the Boolean logic primitives to create a
computer. These so called primitives are merely symbolic.

The
most primitive computer is comprised of only two parts and from these
two parts we can create all others. Those two parts are memory and a
comparator. Some may claim that any practical computer must also have
input and output, but that just is memory, or registers, memory again,
or an ALU, nope that's a comparator.

We can further delineate
memory into two types, read-only and read-write. We need the read-write
type of memory to store temporary values for comparison. For example,
read-write memory could be a toggle or counter. Read-only memory is
convenient for storing tables or a program, however these two examples
are symbolic and not necessary for computation. An example of read-only
memory is pegs in a disc, where the presents of a peg represents a
symbol.

The true heart of a computer is the comparator. A
comparator simply compares two values. One of those two values was read
from memory previously and the other value is read at the current
position in memory.

Now that we have our fundamental blocks we
can start creating all the other complications that are common to modern
computers. However, I'm out of time now so that will have to wait
until later.
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